Humidity is probably too high. Carbon will not activate!
High temperatures and humidity adversely affect on the filtration capacity of activated carbon. It becomes important, therefore to adjust air flow into the filter with temperature fluctuations for effective functioning of the filter. One simple control method makes use of a thermostat to adjust the air flow with temperature variations. Besides temperature variations, extremely high levels of relative humidity also lead to diminishing absorption capacity. A relative humidity of 60%, it has been observed, is the upper limit beyond which filtering performance drops sharply. The relative humidity should therefore not be allowed to exceed this limit.